Receive the latest investigations updates in your inbox

Millennium Tower owners accuse officials of conspiring with the high-rise’s developer to hide evidence that the building was sinking. Jaxon Van Derbeken reports.

Attorneys for the Millennium Tower have filed legal papers accusing officials with the $2 billion Transbay transit project next to the sinking tower of covering up a “breach” of the $58 million protective wall between the two projects.

The developer of the troubled 58-story high-rise has traded accusations with the Transbay Joint Powers Authority since soon after news of th building's sinking broke last year. While Millennium has blamed the multi-agency authority for draining away water and thus destabilizing its foundation, Transbay insists that the developer relied on a faulty foundation not rooted in bedrock and says much of the sinking – about 10 of the 16 inches – occurred before Transbay work began in 2011.

The latest battle is over an elaborate buttress wall built by Transbay with taxpayer money. It extends to bedrock and was designed to limit or prevent groundwater loss from the south side of Millennium’s already sinking foundation. The building has now sunk 16 inches and tilts to the north and west.

Millennium officials said in court filings and in a statement issued Tuesday that the Transbay agency “must take responsibility for the harm” inflicted to the tower by its construction activities – including the faulty wall.

Specifically, Millennium officials say Transbay failed to honor its 2008 agreement to compensate Millennium for foundation damage and even went so far as covering up a failure of the wall it had billed as protecting the Millennium project from damage.

According to the court filing, Transbay officials had learned that the shoring wall had been “breached” but chose to cover that up and even turn off groundwater monitoring equipment.

Records provided to NBC Bay Area from Millennium show that the San Francisco Public Utilities Commission late last year concluded that a half million gallons were drained away – over an unspecified period – that was “attributable to the breach in CDSM [Cement Deep Soil Mixing] wall from neighboring site.”

Neither Millennium’s filing nor city utilities commission records specifies when that alleged breach may have occurred, but there is only one such wall on the southern side of the project.

In a statement, Millennium says Transbay “spent millions of dollars in taxpayer funds on public relations consultants and ‘crisis management’ teams, in an effort to hide the facts and mislead the owners of property in the building, and the people of San Francisco” about its responsibility for damaging the building.

Transbay officials had never acknowledged any breach. They had no immediate comment Tuesday.